Question 941090
Let {{{ t }}} = Tom's age in 2000
Let {{{ g }}} = grandpa's age in 2000
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In 1921, grandpa's age is {{{ g - 79 }}}
( 2000 - 1921 = 79 )
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(1) {{{ g - 79 = 2t }}}
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In 1930, grandpa's age is {{{ g - 70 }}}
( 2000 - 1930 = 70 )
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(2) {{{ g - 70 = 3t }}}
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(1) {{{ t = ( g - 79 ) / 2 }}}
and
(2) {{{ t = ( g - 70 ) / 3 }}}
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{{{ ( g - 79 ) / 2 = ( g - 70 ) / 3 }}}
Multiply both sides by {{{ 6 }}}
{{{ 3*( g - 79 ) = 2*( g - 70 ) }}}
{{{ 3g - 237 = 2g - 140 }}}
{{{ g = 237 - 140 }}}
{{{ g = 97 }}}
grandpa is 97 in 2000
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check:
(1) {{{ t = ( g - 79 ) / 2 }}}
(1) {{{ t = ( 97 - 79 ) / 2 }}}
(1) {{{ t = 18/2 }}}
(1) {{{ t = 9 }}}
and
(2) {{{ t = ( g - 70 ) / 3 }}}
(2) {{{ t = ( 97 - 70 ) / 3 }}}
(2) {{{ t = 27/3 }}}
(2) {{{ t = 9 }}}
OK